/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.evaluation;

import proguard.classfile.*;
import proguard.classfile.attribute.CodeAttribute;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.evaluation.value.*;

/**
 * This ValueFactory tags newly created reference values so they can be traced throughout the execution of a method.
 *
 * @see TracedReferenceValue
 * @see InstructionOffsetValue
 * @author Eric Lafortune
 */
public class ReferenceTracingValueFactory extends SimplifiedVisitor implements InstructionVisitor, ValueFactory {
    private final ValueFactory valueFactory;
    private final boolean preserveTraceValueOnCasts;

    private Value traceValue;

    /**
     * Creates a new ReferenceTracingValueFactory that attaches instruction offset values based on being used as an
     * instruction visitor. This instance preserves trace values in the {@link #cast} method.
     * 
     * @param valueFactory the value factory that creates the actual values.
     */
    public ReferenceTracingValueFactory(ValueFactory valueFactory) {
        this(valueFactory, true);
    }

    /**
     * Creates a new ReferenceTracingValueFactory that attaches instruction offset values based on being used as an
     * instruction visitor.
     * 
     * @param valueFactory the value factory that creates the actual values.
     * @param preserveTraceValueOnCasts specifies whether to preserve the trace value for reference values that are
     *        passed to the {@link #cast} method.
     */
    public ReferenceTracingValueFactory(ValueFactory valueFactory, boolean preserveTraceValueOnCasts) {
        this.valueFactory = valueFactory;
        this.preserveTraceValueOnCasts = preserveTraceValueOnCasts;
    }

    public void setTraceValue(Value traceValue) {
        this.traceValue = traceValue;
    }

    /**
     * Casts a given traced reference value to the given type, either keeping its trace value or setting a new one.
     */
    public TracedReferenceValue cast(TracedReferenceValue referenceValue, String type, Clazz referencedClass,
        boolean alwaysCast) {
        // Cast the value.
        ReferenceValue castValue =
            referenceValue.getReferenceValue().cast(type, referencedClass, valueFactory, alwaysCast);

        // Trace it.
        return new TracedReferenceValue(castValue,
            preserveTraceValueOnCasts ? referenceValue.getTraceValue() : traceValue);
    }

    // Implementations for InstructionVisitor.

    public void visitAnyInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        Instruction instruction) {
        traceValue = null;
    }

    public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        SimpleInstruction simpleInstruction) {
        switch (simpleInstruction.opcode) {
            case InstructionConstants.OP_ACONST_NULL:
            case InstructionConstants.OP_NEWARRAY:
            case InstructionConstants.OP_ATHROW:
                traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.NEW_INSTANCE);
                break;

            case InstructionConstants.OP_AALOAD:
                traceValue = new InstructionOffsetValue(offset);
                break;

            default:
                traceValue = null;
                break;
        }
    }

    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset,
        ConstantInstruction constantInstruction) {
        switch (constantInstruction.opcode) {
            case InstructionConstants.OP_LDC:
            case InstructionConstants.OP_LDC_W:
            case InstructionConstants.OP_NEW:
            case InstructionConstants.OP_ANEWARRAY:
            case InstructionConstants.OP_MULTIANEWARRAY:
                traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.NEW_INSTANCE);
                break;

            case InstructionConstants.OP_GETSTATIC:
            case InstructionConstants.OP_GETFIELD:
                traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.FIELD_VALUE);
                break;

            case InstructionConstants.OP_INVOKEVIRTUAL:
            case InstructionConstants.OP_INVOKESPECIAL:
            case InstructionConstants.OP_INVOKESTATIC:
            case InstructionConstants.OP_INVOKEINTERFACE:
                traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.METHOD_RETURN_VALUE);
                break;

            case InstructionConstants.OP_CHECKCAST:
                traceValue = new InstructionOffsetValue(offset | InstructionOffsetValue.CAST);
                break;

            default:
                traceValue = null;
                break;
        }
    }

    // Implementations for BasicValueFactory.

    public Value createValue(String type, Clazz referencedClass, boolean mayBeExtension, boolean mayBeNull) {
        return trace(valueFactory.createValue(type, referencedClass, mayBeExtension, mayBeNull));
    }

    public IntegerValue createIntegerValue() {
        return valueFactory.createIntegerValue();
    }

    public IntegerValue createIntegerValue(int value) {
        return valueFactory.createIntegerValue(value);
    }

    public LongValue createLongValue() {
        return valueFactory.createLongValue();
    }

    public LongValue createLongValue(long value) {
        return valueFactory.createLongValue(value);
    }

    public FloatValue createFloatValue() {
        return valueFactory.createFloatValue();
    }

    public FloatValue createFloatValue(float value) {
        return valueFactory.createFloatValue(value);
    }

    public DoubleValue createDoubleValue() {
        return valueFactory.createDoubleValue();
    }

    public DoubleValue createDoubleValue(double value) {
        return valueFactory.createDoubleValue(value);
    }

    public ReferenceValue createReferenceValue() {
        return trace(valueFactory.createReferenceValue());
    }

    public ReferenceValue createReferenceValueNull() {
        return trace(valueFactory.createReferenceValueNull());
    }

    public ReferenceValue createReferenceValue(String type, Clazz referencedClass, boolean mayBeExtension,
        boolean mayBeNull) {
        return trace(valueFactory.createReferenceValue(type, referencedClass, mayBeExtension, mayBeNull));
    }

    public ReferenceValue createArrayReferenceValue(String type, Clazz referencedClass, IntegerValue arrayLength) {
        return trace(valueFactory.createArrayReferenceValue(type, referencedClass, arrayLength));
    }

    /**
     * Creates a new ReferenceValue that represents an array with elements of the given type, with the given length and
     * initial element values.
     */
    public ReferenceValue createArrayReferenceValue(String type, Clazz referencedClass, IntegerValue arrayLength,
        Value elementValue) {
        return trace(valueFactory.createArrayReferenceValue(type, referencedClass, arrayLength, elementValue));
    }

    // Small utility methods.

    /**
     * Attaches the current trace value to given value, if it is a reference value.
     */
    public Value trace(Value value) {
        return value.computationalType() == Value.TYPE_REFERENCE ? trace(value.referenceValue()) : value;
    }

    /**
     * Attaches the current trace value to given reference value.
     */
    public ReferenceValue trace(ReferenceValue referenceValue) {
        return traceValue != null ? new TracedReferenceValue(referenceValue, traceValue) : referenceValue;
    }
}
